SBR vulcanization with MBTS•S formulation was found to be inhibited by addition of 5-10phr powdered copper. A similar inhibiting behaviour was observed in SBR vulcanization with CBS•S or TMTD formulation. Such an inhibiting activity was also detected with copper compounds. The activity increased in order of copper dibutyldithiocarbamate_??_CuO<Cu
2O, CuS<Cu(Aco)
2<CuCl
2<cupric stearate_??_Cu. An inhibiting activity of usual powdered metals for vulcanization increased in order of Pb<Fe, Ni, Cr, Co, Mn< Sb, Al<Zn_??_Cu, Hg. The inhibiting activity of copper for SBR vulcanization was found to diminish with addition of nitrogen-containing organic thiol compounds such as zinc-dibutyl-dithiocarbamate, 2-mercaptobenzothiazole (MBT), 6-dibutylamino-1, 3, 5-triazine-2, 4-dithiol or trithiocyanuric acid (TTCA). TTCA which is trithiol was most effective. Thiol groups of TTCA react readily with copper to form a deactivated chelating compound as well as with SBR in presence of MBTS in the vulcanizing compound. Such a coupling effect between copper and SBR was hardly observed with monothiol compounds such as MBT. Thus, a composite of vulcanized SBR and powdered copper with an excellent mechanical property was obtained through the following composition: SBR 100, powdered copper 100, HAF 50, ZnO 5, S 0.5, TTCA 6, MBTS 6.6, antioxidant D 2phr.
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